Field of the Invention
The present invention relates to a cut sheet feeder for use with the image forming apparatus such as a copier or a printer, the feeder feeding the apparatus with cut sheets of recording paper.
Description of the Related Art
The image forming apparatus is most often used to record images on a large number of cut sheets of the same size which are fed continuously. But occasionally, it is desired to interrupt the ongoing process of image printing involving many cut sheets so as to insert image printing of a different kind typically on a smaller number of sheets. Some of the conventional cut sheet feeders for use with the image forming apparatus have mechanisms that meet the requirements for the on-demand inserted printing.
Such conventional cut sheet feeders have a plurality of sheet feed mechanisms positioned near the sheet feed table or sheet cassette assembly, each mechanism comprising its dedicated pick-up rollers, guide plates and other related parts. When the operator selects a desired sheet type, the corresponding sheet feed mechanism is activated. The activated mechanism picks up cut sheets one by one from the applicable sheet feed table or from the corresponding sheet cassette and feeds them into a position inside the image forming apparatus.
The conventional cut sheet feeder of the above-mentioned type has as many sheet feed mechanisms as the number of the sheet feed tables or the sheet cassettes that are mounted in advance of feed operation. The cut sheet feeder also has a plurality of sheet transport routes for guiding cut sheets from the multiple storage locations via rollers to a common feed position. These features combine to make the cut sheet feeder bulky, complex, and thus prone to feed-related troubles.
In view of these drawbacks of the prior art, the inventors of this invention came up with a cut sheet feeder having a single sheet feed mechanism to which any one of a plurality of sheet feed tables carrying many cut sheets or of sheet cassettes containing different sizes of cut sheets is positioned as desired.
But because the cut sheet feeder of the above type requires one of its sheet feed tables or sheet cassettes to be moved to a single sheet feed position, arrangements need to be made so that one table or cassette will not interfere during movement with any other table or cassette. In addition, this cut sheet feeder needs to be constructed so that cut sheets on the sheet feed table or in the sheet cassette selected and fed quickly, simply and smoothly to the sheet feed mechanism with the aid of appropriate electrical control means.
With the sheet cassettes made detachable, the procedure of on-demand inserted printing is made simpler, but there are still measures to be taken to ensure that the operator carries out operations correctly and that the whole system runs with safety and without malfunction.